She comes to drop off a rent check with Aidan alone in the house, and his lack of blood and Beth and Holly's taunting cause him to come off as odd. Kat later goes back to the house while Erin is in the hospital, and Aidan helps her fix her plumbing, while also revealing her interest in early American history, to which Aidan is well acquainted. The two hit it off, and later he asks her out on a date, and she agrees. Aidan tries to break it off with her, for fear of retaliation from Nora, but he continues to see her until he is approaced and imprisoned by Liam. Kat tries to find out what has happened, prompting Josh's rescue, and after Aidan is infected, Nora invites her over so they can see each other one last time.
After Aidan is cured, he approaches her at the university and passionately kisses her, while remembering his |wife's words to him centuries before that he should seek out new love when he finds it. After a disastrous date at the Boston Rare Book Archives where Kat comes across her ex-boyfriend Jeff Westin and his new date Marissa, a college student who seems to be in the same situation Kat was in years ago, they reveal their plans for the future, in which Kat wants to have a family of her own, even though Aidan cannot provide this for her. They start to get intimate, only for Aidan to back away when the bloodlust overcomes him. Outside, after drinking from a blood bag he has with him, goes back to Kat and they sleep together. However, Aidan awakes in an alley hours later, unknowingly having killed and turned Jeff Westin. Kat is invited for Josh and Nora's wedding, where she is upset that Aidan left her alone after their first night together, but Aidan later apologizes by saying it had been a long time since he had last been intimate with someone and got scared, but promised that it would not happen again and they end up on good terms, with Aidan later admitting that Kat is his girlfriend.
Kat later participates in the wedding, being one of Nora's bridesmaids alongside Emily and a spectral Sally.